Item Coding — Conversion between Item Labels and Column IDs
Provides the generic functions and the S4 methods to translate between the binary representation in the itemMatrix format (used in transactions, rules and itemsets), item labels and numeric item IDs (i.e., the column numbers in the binary representation).
encode(x, ...) ## S4 method for signature 'list' encode(x, itemLabels, itemMatrix = TRUE) ## S4 method for signature 'character' encode(x, itemLabels, itemMatrix = TRUE) ## S4 method for signature 'numeric' encode(x, itemLabels, itemMatrix = TRUE) recode(x, ...) ## S4 method for signature 'itemMatrix' recode(x, itemLabels = NULL, match = NULL) decode(x, ...) ## S4 method for signature 'list' decode(x, itemLabels) ## S4 method for signature 'numeric' decode(x, itemLabels)
x |
a vector or a list of vectors of character strings
(for |
itemLabels |
a vector of character strings used for coding where
the position of an item label in the vector gives the item's column ID.
The used |
itemMatrix |
return an object of class |
match |
an |
... |
further arguments. |
encode
converts from readable item labels to an itemMatrix using a
given coding. With this method it is possible to create several compatible
itemMatrix
objects (i.e., use the same binary representation for
items) from data.
recode
recodes an itemMatrix object so its coding is compatible
with another itemMatrix object specified in match
(i.e., the colums are reordered to match).
decode
converts from the colun IDs used in the temMatrix representation to
item labels. decode
is used by LIST
.
recode
always returns an object
of class itemMatrix
.
For encode
with itemMatrix = TRUE
an object
of class itemMatrix
is returned.
Otherwise the result is of the same type as x
, e.g., a
list or a vector.
Michael Hahsler
data("Adult") ## Example 1: Manual decoding ## get code iLabels <- itemLabels(Adult) head(iLabels) ## get undecoded list and decode in a second step list <- LIST(Adult[1:5], decode = FALSE) list decode(list, itemLabels = iLabels) ## Example 2: Manually create an itemMatrix data <- list( c("income=small", "age=Young"), c("income=large", "age=Middle-aged") ) iM <- encode(data, iLabels) iM inspect(iM) ## use the itemMatrix to create transactions as(iM, "transactions") ## Example 3: use recode ## select first 100 transactions and all education-related items sub <- Adult[1:100, itemInfo(Adult)$variables == "education"] itemLabels(sub) image(sub) ## recode to match Adult again sub.recoded <- recode(sub, match = Adult) image(sub.recoded) ## Example 4: manually create 2 new transaction for the Adult data set ## Note: check itemLabels(Adult) to see the available labels for items twoTransactions <- as(encode(list( c("age=Young", "relationship=Unmarried"), c("age=Senior") ), itemLabels = itemLabels(Adult)), "transactions") inspect(twoTransactions) ## Example 5: manually create a rule and calculate interest measures aRule <- new("rules", lhs = encode(list(c("age=Young", "relationship=Unmarried")), itemLabels = itemLabels(Adult)), rhs = encode(list(c("income=small")), itemLabels = itemLabels(Adult)) ) quality(aRule) <- interestMeasure(aRule, measure = c("support", "confidence", "lift"), transactions = Adult) inspect(aRule)
Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.